It is often desirable to provide a hydrophilic coating (e.g., anti-fog coating) on a substrate such as an automotive windshield, automotive window, automotive mirror, architectural mirror, bathroom mirror, architectural window, or the like. Such coatings may reduce the likelihood of water drops deposited on the substrate taking globular shape(s), thereby permitting visibility to be improved. In other words, hydrophilic coatings function to reduce bead-like condensation on substrate surfaces (e.g., on the interior surface of an automotive windshield or window, IG window unit, or the like). In essence, a hydrophilic coating can reduce the formation of many tiny droplets of liquid which can scatter light on a surface (i.e., make condensation on a surface film-wise as opposed to droplet-wise).
Unfortunately, certain hydrophilic coatings are not as durable and/or hard as would otherwise be desired and thus are not efficient from a practical point of view for applications such as automotive windshields and/or other types of windows or
U.S. Pat. No. 6,713,179, hereby incorporated herein by reference, discloses a layer comprising diamond-like carbon (DLC) that is treated with ultraviolet (UV) radiation in order to cause it to become hydrophilic (i.e., the UV exposure causes the contact angle θ of the layer to decrease). While this process of making a hydrophilic DLC inclusive layer works well, it takes much time. The example in U.S. Pat. No. 6,713,179 states that the DLC was treated with QUV for 86 hours in order to cause the contact angle θ of the DLC to drop from 73.47 degrees to 19.12 degrees (i.e., this contact angle reduction of 74% took 86 hours). It would be desirable if a DLC inclusive layer could be made to be hydrophilic via a less time-consuming process.
U.S. Patent Document 2004/0067363 discloses treating DLC with an ion beam and hot water in order to cause contact angle θ to be reduced. In such systems, the ion beam treatment is often performed as the last vacuum step in a coater or the like, and subsequent exposure to hot water can be performed in an exit bath. However, since vacuum space is valuable and capital intensive, and it would be desirable if a system for causing contact angle θ of DLC to be reduced could be developed which could optionally be performed in an ambient atmosphere where no vacuum is required.
In view of the above, it is apparent that there exists a need in the art for one or more of (i) a coated article (e.g. coated glass or plastic substrate) having hydrophilic properties, and/or a method of making the same, (ii) a protective hydrophilic coating for window and/or mirror substrates that is somewhat resistant to scratching, damage, (iii) a technique for causing contact angle θ of DLC to be reduced which may be performed in an ambient atmosphere where no vacuum is required, and/or (iv) a process for reducing a contact angle of DLC in a less time-consuming manner.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.